Despite the feverish attempts of the Arab infidels to suppress the call of truth, the young Muslim community began to grow in numbers, as more and more people flocked to the call of Islam.
The Prophet's mission in Makkah can thus be classified under the following two periods:
The Secret Call
At first the Messenger of Allah called people to Islam secretly. He began with his immediate kinsmen, the Bani Hashim, explaining to them his divine mission. For three consecutive days he discoursed with them, without much success, and only his young cousin Ali [a], stood up every time saying 'I bear witness Muhammad is the Messenger of Allah.' The other members of his clan either mocked at him or remained silent, perhaps needing time to ponder over his words.
Without feeling the least discouraged, Muhammad [s] continued his work, encountering individuals and inviting them to Islam. By and large, the devoted group of Muslims increased around him, and he selected a secret secluded spot, to assemble the faithful and teach them the principles of Islam and the verses of Qur'an as they were gradually revealed. When the number of Muslims had reached 40, Almighty Allah ordered His Messenger to shun the garment of secrecy and make public the invitation to Islam.
The Public Call
As the number of committed Muslims began to grow, Almighty Allah commanded His Prophet to publicly announce the call to Islam. Some of the notable converts at this stage included Muhammad's [s] kinsmen such as Ja'far bin Abi Talib, Ubaidah bin Hareth bin Abdul Muttalib and etc...
The growing presence of such a strong Muslim community in their midst naturally annoyed the obstinate polytheists, who felt increasing danger to their hegemony. The infidels, who had no logic to defend their worship of manmade objects and stop the awakened masses from flocking toward the light of Islam, resorted to torture and other methods of oppression against the fledgling Muslim society. Bilal the Abyssinian, Suhaib the Roman, Khabab bin Art, and others underwent the most rigorous forms of torture at the hands of arrogant Jahiliyah.
The Mission Continues
Despite the hardships, the infant community of Islam stood steadfast in its beliefs. The Prophet's wife Khadija bint Khwailid who was blessed with a large fortune, put all her wealth and property at her husband's disposal, to help the spread of Islam. The personality of Abu Talib, Muhammad's [s] uncle, who was respected and admired by the Quraish, was instrumental in keeping the polytheist Arabs at a distance, and they were afraid of doing any bodily harm to the Prophet. The Prophet continued to teach the young Muslim community, the divine revelations and the basic tenets of Islam. His most enthusiastic disciple and student was none other than his young cousin, Ali, who was the closest personality to Muhammad [s].
A point to note is that while all the early Muslims were mature people and had experienced the fruits and bitterness of growing up among the idols of Arabia, it was only Ali, who entrusted to his cousin's guardianship years before the call of Islam, was like Muhammad [s] - of a pristine pure personality and far removed from contemporary corruption. Perhaps it was divine providence that Ali should be groomed personally by the last and greatest Messenger to mankind. Hence, the young Ali imbibed all the knowledge directly from the Prophet himself.
Consequently the Da'wah (Islamic Call) of the Prophet falls into two clearly discernible periods as follows:
1. The period in Makkah, beginning with the age of 40 till his emigration to Madina 13 years later.
2. The period at Madina, beginning with the Prophet's historical arrival till his sad demise 10 years later at the age of 63.